Non-orthogonal multiple access (NOMA) is a wireless bandwidth sharing technique where multiple users can concurrently occupy channel bands, with each user optionally encoded by error detection/correction coding, e.g., forward error correction (FEC), and can be sorted at a receiver, by the receiver applying for example successive interference cancellation (SIC) or other known techniques. This contrasts to multiplexing techniques such as time-division multiple access (TDMA), frequency-division multiple access (FDMA), and orthogonal frequency-division multiple access (OFDM), which generally allocate per-user frequency bands, or time slots, or both.
However, for certain NOMA schemes, the FEC code rate needs to be low to provide acceptable performance in many applications. This can limit per user spectral efficiency. A technical need therefore exists for increasing per user spectral efficiency in those systems.